Kodachrome - Processing of Kodachrome Films

Processing of Kodachrome Films

Kodachrome, and other non-substantive films, required complex processing that could not practicably be carried out by amateurs. The process underwent four significant alterations since its inception. The final version of the process, designated K-14, was introduced in 1974. The process was complex and exacting, requiring technicians with extensive chemistry training and large, complex machinery.

The first step in the process was the removal of the antihalation backing with an alkaline solution and wash. The film was then developed using a developer containing phenidone and hydroquinone, which formed three superimposed negative images, one for each primary color. After the first developer was washed out, the film underwent re-exposure and redevelopment. Re-exposure fogged the silver halides that were not developed in the first developer. A color developer then developed the fogged image, and its exhaustion products reacted with a color coupler to form a dye in the color complementary to the layer's sensitivity. The red-sensitive layer was re-exposed through the base of the film with red light, then redeveloped forming cyan dye. The blue-sensitive layer was re-exposed through the emulsion side of the film with blue light, then redeveloped forming yellow dye. The green-sensitive layer was redeveloped with a developer that chemically fogged it and formed magenta dye. After color development, the metallic silver was converted to silver halide using a bleach solution. The film was then fixed, making these silver halides soluble and leaving only the final dye image. The final steps were to wash the film to remove residual chemicals which might cause deterioration of the dye image, then to dry, cut, and mount the film in slide frames.